Cesium Complex of an Unsymmetrical Calix[4]crown-dibenzocrown-6

An unsymmetrical calix[4]-bis-crown ether having both conventional crown-6 and dibenzocrown-6 rings in a fixed 1,3-alternate conformation was synthesized with good yield by the reaction of a monocyclic calix[4]crown-6 with dibenzodimesylate in the presence of cesium carbonate. The cesium ion selectivity among alkali metal ions increased compared to symmetrical calix[4]-bis-crown-6. The solid state structureof the ligand-cesium complex illustrates a 1:2 complex ratio. On the contrary, insolution, e.g., extraction equilibrium and ¹H NMR experiment gave a 1:1 complex ratio. From the result of the chemical shift change upon metal ion complex, the cesium ion seems to prefer the dibenzocrown loop to the conventional crown-6 ring.     

Spectrophotometric study of the supramolecular complexes of [60]- and [70]Fullerenes with biscalix[6]arene and crown[4]calix[6]arene

[60]- and [70]Fullerenes have been shown to form 1:1 supramolecular complexes with bis[2-(5,11,17,23,29,35-hexa-tert-butyl-37,38,39,40,41-pentahydroxycalix[6]arenyl-oxy ethyl ether) (1) and 5,11,17,23,29,35-hexa-tert-butyl-37,38,40,41-tetra hydroxyl-39,42-(crown-4)calix[6]arene (2) in CHCl3 medium by electronic absorption spectroscopy. Formation constants (K) of the complexes of [60]- and [70]fullerenes with 1 and 2 have been determined at room temperature from which free energy of formation values of the complexes have been estimated. The very high formation constant value of [60]fullerene/1 complex (5900 dm3 mol-1) in indicative of formation of inclusion complex. Moreover, PM3 calculations reveal that intermolecular interaction between [60]fullerene and 1 proceeds through quite deep energy molecular orbital.     

Novel Cesium‐Selective Electrodes Based on Lipophilic 1,3‐Bisbridged Cofacial‐calix[6]crowns

Five bisbridged calix[6]crowns have been investigated as Cs⁺ ionophore in PVC membrane electrodes. As ionophores, three 1,3‐bisbridged calix[6]crown‐4‐ethers( I–III ), 1,3‐bisbridged calix[6]crown‐5‐ether( IV ), and 1,3‐bisbridged calix[6]crown‐6‐ether( V ) have been evaluated. The membranes all give good Nernstian response in the concentration range from 1×10^?7 to 1×10^?1 M of cesium ion. The best detection limits (?log aequation/tex2gif-inf-1.gif=7.08–7.36) are obtained for electrode membranes containing 1,3‐bisbridged cofacial‐calix[6]crown‐4‐ethers( I‐III ), and the values are the lowest compared with those reported previously. The highest selectivity coefficients [ 3.74(Cs/K), 2.63(Cs/Rb)] are obtained for the membrane of 1,3‐bisbridged calix[6]crown‐4‐ether( II ), and these values are also the highest compared with previous reports for Cs⁺‐ISEs. The highest selectivity towards cesium ion is attributed to the geometrically cofacial positions of two crown‐ethers in calix[6]crowns in order to provide the complex of cesium ion and eight oxygens of cofacial crowns.     

Syntheses and Metal-ion Binding Properties of Calix[4]arene Derivatives Containing Soft Donor Atoms: Highly Selective Extraction Reagents for Ag+

A series of calix[4]arene derivatives containing N or S atoms atthe lower rim were synthesized by etherification of OH groups and their metal-ion extraction abilities were studied. The extraction selectivity for Ag⁺ over other ions with these novel receptors was outstanding. Among these ligands, calix[4]arene podand, which possessed two linear ligands, has shown better binding ability with Ag⁺ than calix[4]crowns.     

Synthesis and Cesium Binding Affinity of New 25,27-Bis(alkyloxy)calix[4]arene-crown-6 Conformers in Relation to the Alkyl Pendent Moiety

The preparation of new 25,27-bis(alkyloxy)calix[4]arenes-crown-6 in the cone, partial-cone and 1,3-alternate conformation is reported. We have also investigated the alkylation of the cone monoalkylated calix[4]arene-crown-6 achieved using Cs 2 CO 3 . This reaction afforded a mixture of cone and partial-cone calix[4]arenes-crown-6 having an alkyl chain anti or syn to the polyether ring. Conformations have been probed using 1 H, 13 C, 2D-NMR and NOESY analysis, and using X-ray crystallography. Extraction experiments using a two-phase solvent method involving cesium picrate were performed for these newly synthesized conformers. They reveal and confirm the strong preference for the 1,3-alternate conformers. The affinity of 1,3-alternate calixarenes for Cs + has been assessed by complexation measurements (log g ) using a spectrophotometric technique. No significant Cs + extraction difference was observed in relation to the nature of the alkyl chains on the aromatic rings. 1 H NMR studies of the 1,3-alternate calixarene Cs + complexes confirms the cation's spacial position between the two aromatic rings, due to cation- ~ interactions.     

Online recovery of radiocesium from soil,cellulose and plant samples by supercritical fluid extraction employing crown ethers and calix-crown derivatives as extractants

Two crown ethers (CEs) viz. dibenzo18crown6, and dibenzo12crown7 and three calix-crown derivatives viz. (octyloxy)calix[4]arene-mono-crown-6 (CMC), calix[4]arene-bis(o-benzocrown-6) (CBC), and calix[4]arene-bis(naphthocrown-6) (CNC) were evaluated for the recovery of ¹³⁷Cs from synthetic soil, cellulose (tissue paper), and plant samples by supercritical fluid extraction (SFE) route. CEs showed poor extraction of ¹³⁷Cs from soil matrix. SFE experiments using 1 × 10^?3 M solutions of CMC, CBC and CNC in acetonitrile at 3 M HNO₃ as modifiers displayed better extraction of ¹³⁷Cs, viz. 21(±2) % (CMC), 16.5(±3) % (CBC), and 4(±1) % (CNC). It was not possible to recover ¹³⁷Cs quantitatively from soil matrix. The inefficient extraction of ¹³⁷Cs from soil matrix was attributed to its incorporation into the interstitial sites. Experiments on tissue papers using CMC showed near quantitative ¹³⁷Cs recovery. On the other hand, recovery from plant samples varied between 50(±5) % (for stems) and 75(±5) % (for leaves).     

N-硫脲基套索杯[4]冠醚与四硫脲基杯[4]芳烃的合成

控制反应物的物质的量比, 杯式对叔丁基杯[4]-1,3-二乙酸乙酯衍生物1与5或50倍二乙烯三胺反应, 分别得到杯[4]氮杂冠醚2和开链的氮杂杯[4]芳烃衍生物3. 化合物2和3进一步与异硫氰酸苯酯反应得到首例侧链含硫脲基的套索杯[4]氮杂冠醚4和含4个硫脲基的杯[4]芳烃衍生物5, 产率为92%和87%. 新化合物的结构与构象经元素分析、红外、质谱、核磁共振谱等表征证实.     

Synthesis of New Calix[4]arenes Functionalizated by Acetylhydrazide Groups

A series of new calix[4]phenols, calix[4]resorcinols and calix[4]pyrogallols with acetylhydrazide substitutes has been␣synthesized with high yields by hydrazinolysis of ester group containing calix[4]arenes. The synthesized calix[4]phenols adopt the cone conformation while the calix[4]resorcinol and calix[4]pyrogallol derivatives prefer the boat conformation. The amide fragment of the hydrazide groups predominantly exists in the trans-conformation. The binding ability of synthesized calix[4]arenes toward transition and alkali metals by solvent extraction has been investigated.     

一锅法合成含两种桥联链的杯[4]双冠醚和双杯[4]冠醚

报道了"一锅法"合成含两种桥联链的新型杯[4]双冠醚和双杯[4]冠醚.杯[4]芳烃先与N,N’-乙撑基-二(2-氯乙酰胺)发生"1+1"缩合反应,然后直接加入三甘醇双对甲苯磺酸酯继续进行"2+2"缩合反应,合成了含两种桥联链的新型双杯[4]冠醚4.按照相似程序,杯[4]芳烃先后与N,N’-乙撑基-二(2-氯乙酰胺)、溴乙酸乙酯和二乙烯三胺反应,得到含两种桥联链的新型杯[4]双冠醚5.化合物5进一步与异硫氰酸苯酯反应合成带硫脲支链的杯[4]双冠醚6.所有新化合物的结构与构象经元素分析、质谱、核磁共振谱等表征证实.     

单氧代-二硒烷基-1, w-二氧取代杯[4]衍生物的合成,结构及萃取性能研究

Novel macrocyclic monooxa-diselkylene-1,ω-dioxy substituted calix[4]arene derivatives 1a-5a were synthesized by the reaction of calix[4]arene dibromides 1-5 with the disodium salt of bis（2-selenylethyl）ether in the yields between 28% and 64%. Their structures were characterized by proton and carbon NMR spectra. X-Ray structure analysis of la further confirmed the cone conformation of compounds 1a-5a. An interesting host-guest complex of la with dichloromethane via CH/π and C1/π interactions was elucidated. Extraction experiments showed that these novel monooxa-diselkylene-1,ω-dioxy substituted calix[4]arene derivatives 1a-5a had strong extraction ability towards mercury ion. The interaction of Hg^2＋with the calix ligand has also been investigated by 1^H NMR titration.     

Stilbene-bridged 1,3-alternate calix[4]arene crown ether for selective alkali ion extraction

A series of stilbene-bridged calix[4]arenes was synthesized through an intramolecular reductive McMurry coupling of bisbenzaldehyde calix[4]arene in high yields. Tetra- and pentaethylene glycol chains were tethered to the phenolic groups of calix[4]arene to form stilbene-bridged calix[4]arene crown-5 and crown-6, respectively. The presence of stilbene bridge over the calix[4]arene rim effectively prevented the connection of the polyether chains in the cone conformation resulting in the exclusive formation of 1,3-alternate stilbene-bridged calix[4]arene crown product. Compared to the cone analogues, the 1,3-alternate calix[4]arene crown ethers showed a greater extraction ability and selectivity toward Cs⁺.     

Selective functionalization at the small rim of calix[6]arene. Synthesis of novel non-symmetrical N3, N4 and N3ArO biomimetic ligands

Eight novel calix[6]arene-based biomimetic ligands for transition metal ions have been synthesized. They display a non-symmetrical N₃, N₄ or N₃ArO binding core that mimics enzyme active sites presenting histidine and tyrosine residues. The key step for their synthesis is the mono-alkylation at the small rim of the C_3v symmetrical trimethyl ether derivative of tBu-calix[6]arene with N-Boc-2-chloroethylamine to yield a novel calix[6]arene synthon. Its combined O-alkylation with a chloromethyl aromatic amine and N-deprotection or alkylation or reductive alkylation with a salicylaldehyde derivative yielded the calix[6]arene-based ligands with mixed N/O donors.     

Ab initio and density functional studies of cooperative hydrogen bonding in calix[4]-and calix[6]arenes

The cone conformation of C ₄ symmetry is shown by the Hartree-Fock method (3-21G basis) to be the predominant conformer of calix[4]arene; the compressed cone of C ₂ symmetry is the major conformer of calix[6]arene. Using quantum chemical methods we calculated hydrogen bond cleavage energies for calix[4]-(ab initio and density functional methods) and calix[6]arene (ab initio), and also for the complex of calix[4]arene with carbon disulfide. These energies along with structural data point to the cooperative effect of hydrogen bonds. The results of these studies provided an explanation to the greater conformational lability of calix[6]arene compared with calix[4]arene molecules. It is also predicted that the nucleophilic substitution reaction involving calix[6]arene in the presence of weak bases and in aprotic solvents, as well as in the gas phase, will occur via diastereomeric transition states.     

Ion Complexation Properties of Calix[6]Arene Derivatives: I. 1,4-Calix[6]Crown-4 Derivatives

Abstract

A series of 1,4-p-tert-butyl-calix[6]crown-4 tetraesters, tetraamides, tetraacids with defined conformation have been synthesized, and their complexation properties towards metal ions and alkyl ammonium ions were investigated systematically. It was found that 1,4-p-tert-butyl-calix[6]crown-4 tetraethylester (3a) and 1,4-p-tert-butyl-calix[6]benzocrown-4 tetramethyl-ester (4b) show high selectivity towards Na⁺, Li⁺, respectively and all of them exhibit high complexation abilities towards Et₂NH₂ ⁺ cation.     

Synthesis, NMR, X-ray structural analyses and complexation studies of new Ag selective calix[4]arene based dipodal hosts—a co-complexation of neutral and charged species

New podands based on the p-tert-butylcalix[4]arene unit with substitution at the lower rim incorporating imine units, have been synthesized in high yield by simple condensation method. These podands have been shown to extract and transport Ag⁺ selectively over alkali, alkaline earth metal cations, Zn²⁺, Pb²⁺ and Hg²⁺ ions, from neutral aqueous phase to organic phase. In all the ligands the calix unit has been found to be present in a cone conformation except for the one having pyridine as end group, at the ortho position. It has been isolated in two conformations; cone and 1,2-alternate. To the best of our knowledge, this may be the first 1,3-lower rim substituted calix[4]arene to exist in a 1,2-alternate conformation and is among a few known compounds with this conformation in the general class of calix[4]arenes. A complex of this ligand, which happens to be the highest extractant of Ag⁺ has been isolated and characterized using mass, ¹H and ¹³C NMR spectroscopy's and elemental analysis. The spectroscopic evidence and molecular modelling studies performed on the complex suggest a participation of the imine and pyridine nitrogens and two of the ether oxygens in coordination to the metal ion. The X-ray crystal structures of three of the ligands establish the formation of inclusion complexes with polar acetonitrile solvent molecules. The ¹H and ¹³C NMR spectra of all the compounds, taken in CDCl₃, show the presence of acetonitrile molecules in the cavity of the calix[4]arene, indicating inclusion of the neutral guest molecules in the solution phase as well. For one of the podands X-ray crystal structure has shown a formation of clatharate complex of chloroform with the ligand which has rarely been found in the case of calix[4]arenes.     

杯芳烃与NO2硝化反应的研究

系统地研究了羟基杯[n]芳烃、甲氧基杯[n]芳烃和对特丁基杯[n]芳烃(n＝4, 6, 8)与NO₂气体的硝化反应, 发现可以成功地得到25,26,27,28-四羟基杯[4]芳烃、37,38,39,40,41,42-六羟基杯[6]芳烃以及25,26,27,28-四甲氧基杯[4]芳烃的对位全硝化产物, 产率分别为90%, 70%和40%; 尤其是25,26,27,28-四羟基杯[4]芳烃与NO₂的反应20 min即可完成. 认为共振式酚氧负离子结构是影响该类硝化反应的关键, 并对反应机理进行了探讨.     

Cesium-ion selective electrodes based on calix[4]arene dibenzocrown ethers

Four calix[4]arene dibenzocrown ether compounds have been prepared and evaluated as Cs(+)-selective ligands in solvent polymeric membrane electrodes. The ionophores include 25,27-bis(1-propyloxy)calix[4]arene dibenzocrown-6 1, 25,27-bis(1-alkyloxy)calix[4]arene dibenzocrown-7s 2 and 3, and 25,27-bis(1-propyloxy)calix[4]arene dibenzocrown-8 4. For an ion-selective electrode (ISE) based on 1, the linear response concentration range is 1x10(-1) to 1x10(-6) M of Cs(+). Potentiometric selectivities of ISEs based on 1-4 for Cs(+) over other alkali metal cations, alkaline earth metal cations, and NH(4)(+) have been assessed. For 1-ISE, a remarkably high Cs(+)/Na(+) selectivity was observed, the selectivity coefficient (K(Cs,Na)(Pot)) being ca. 10(-5). As the size of crown ether ring is enlarged from crown-6 (1) to crown-7 (2 and 3) to crown-8 (4), the Cs(+) selectivity over other alkali metal cations, such as Na(+) and K(+), is reduced successively. Effects of membrane composition and pH in the aqueous solution upon the electrode properties are also discussed.     

Anion influence on extraction and transport of amino acid methyl esters by functionalised calix[4]arene

The liquid–liquid extraction of a series of amino acid methyl esters has been carried out with functionalised calix[4]arene (5,11,17,23-tetrakis(N-methylpiperazino)-25,26,27,28-tetrahydroxycalix[4]arene) from an aqueous phase into a chloroform phase as ion pairs in the presence of picrate ion or tropaeolin 00 as counter ion in order to study the molecular recognition properties of this receptor. The active transport assisted by pH gradient of amino acids as ion pairs through liquid membrane employing the functionalised calix[4]arene as carrier has been investigated. The results showed that the receptor exhibits good extractability towards amino acids and it can also act as carrier through liquid membrane aiming to the separation of amino acids. It was highlighted that the anion nature used as counter ion, the structure of calix[4]arene, and the structure of amino acids are responsible for the experimental results obtained. High yields in both amino acids extraction and transport were obtained for picrate ion used as counter ion.     

新型席夫碱基杯[4]冠醚衍生物的合成

杯[4]-1,3-二酯衍生物与水合肼反应后再与二水杨醛二甘醚发生"1 1"分子间缩合,高产率合成了新型席夫碱基杯[4]冠醚衍生物,其结构经1HNMR,IR,MS和元素分析表征。     

Tri- and pentacalix[4]pyrroles: synthesis, characterization and their use in the extraction of halide salts

Calixpyrrole-based oligomeric compounds were synthesized by "click chemistry" from the corresponding alkyne- and azide-functionalized calix[4]pyrroles. Calix[4]pyrrole 3, possessing an alkyne functional group, was prepared through a mixed condensation of pyrrole with acetone and but-3-ynyl 4-oxopentanoate. Another alkyne-group-containing calix[4]pyrrole 5 was obtained by treatment of 4'-hydroxyphenyl-functionalized calixpyrrole 4 with propargyl bromide. Tetrakis(azidopentyl)-functionalized calix[4]pyrrole 7 was synthesized by reacting NaN(3) with tetrabromopentyltetraethylcalix[4]pyrrole 6, which was prepared through a condensation reaction of pyrrole and 7-bromohept-2-one. Oligomeric calixpyrrole compounds were found to be capable of extracting tetrabutylammonium chloride and fluoride salts from aqueous media. Extraction abilities of the oligomeric compounds were monitored by NMR and UV/Vis spectroscopy and thermogravimetric analysis.